Table 1 Optimization of the reaction conditions^a

Troc 2,2,2-trichloroethoxycarbonyl, DCM dichloromethane, THF tetrahydrofuran, DMF N,N-dimethylformamide, TBME tert-butyl methyl ether, NR no reaction.
^aUnless otherwise noted, the reaction was carried out on a 0.1 mmol scale: to a solution of 1a (39.9 mg, 0.10 mmol), 2a (24.0 mg, 0.15 mmol), and 3a (16.1 mg, 0.10 mmol) in indicated solvent (1.0 mL), was added a premixed solution of copper Cu(CH₃CN)₄PF₆ (1.8 mg, 5.0 mol%) and ligand L (6.0 mol%) in the same solvent (1.0 mL) in one portion under argon atmosphere at 30 ^oC. The reaction mixture was stirred for additional 24 h under these conditions.
^bThe yields of 5a were determined by ¹H NMR spectroscopic analysis of the crude reaction mixture using 4-nitrobenzaldehyde as the standard.
^cThe ee values were determined by chiral high-performance liquid chromatography (HPLC) analysis. ^dThe data in parentheses are yields of Csp²-H insertion product 4a.
^e4Å MS (50 mg) and DIPEA (10 mol%) were used as additive.
^fIsolated yield of 5a.

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